理论空燃比天然气汽车尾气中H2O和O2对CH4与NO反应的影响

共沉淀法制备CeZrYLa+LaAl 复合氧化物载体, 等体积浸渍法制备了Pt 催化剂, 用于研究理论空燃比天然气汽车(NGVs)尾气净化反应中CH₄与NO的反应规律. 并考察了10% (体积分数, φ)H₂O和计量比O₂对CO₂存在时的CH₄+NO反应的影响. 结果表明: 对于不同条件下的NO+CH₄反应, 主要生成N₂和CO₂, 高温区有CO生成. 低温区无O₂时可以生成N₂O, 有O₂时可以生成NO₂; 添加10% (φ)的H₂O后, CH₄ 转化活性降低, NO转化活性基本不变, 这是由于H₂O减弱了CH₄与CO₂的重整反应, 但是对CH₄与NO的反应基本没有影响; 添加计量比的O₂后, CH₄转化活性提高, 而NO转化活性降低, 这是由于O₂和NO之间存在竞争吸附, CH₄被O₂氧化为主要反应, 从而减弱了NO的转化; 同时添加计量比的O₂和10% (φ) H₂O, CH₄与CO₂的重整反应受到抑制,CH₄与NO的反应、甲烷蒸汽重整反应和甲烷被O₂氧化反应同时发生, CH₄和NO的转化活性均提高.     

不同气氛下煤连续热解产物的分配规律及产品品质分析

在连续进出料的流化床中研究了热解温度为850 ℃时,含有O₂、H₂、CO、CO₂、CH₄的反应气氛对热解产物分配规律及产品组成的影响。采用Raman、BET等测试方法对不同热解气氛下制得半焦的品质进行了评价,结合热重分析了影响半焦反应活性的因素。结果表明,无O₂气氛下,H₂与CO₂存在时降低了焦油产率,而CO与CH₄促进了焦油的生成。CH₄的裂解析碳使半焦产率上升。O₂的加入使CO₂、CO含量明显增加,半焦及焦油产率降低。N₂中引入O₂时,PAHs含量降低。CH₄促进了烷基萘与苯类的生成,CO则抑制酚类裂解生成苯类。CO₂的气化作用促进了微孔的生成,相应地,半焦的比表面积快速增加,半焦的反应活性也最高。CO歧化与CH₄热裂解产生的析碳堵塞了部分孔道,降低了比表面积。H₂与CH₄所产生的氢自由基能渗透到半焦内部,引起半焦结构的缩聚,进而影响氧化反应活性。     

生物油部分氧化气化制备合成气研究

以生物油为原料,在常压和空气氛围下进行非催化部分氧化气化实验制备合成气,考察了气化温度、氧油比对合成气形成特性及合成气品质的影响,并对生物油非催化部分氧化气化制备合成气的主要反应过程进行了讨论。结果表明,升高温度可以促进生物油经非催化部分氧化气化制合成气过程中相关转化反应的进行,合适的氧油比有利于合成气的增加。当温度为1 050℃,空气量为0.2 L/min,进料量为72 g/h时,生物油经部分氧化产生的气体中H₂含量最高,CH₄、CO和CO₂很少;H₂/CO和H₂/(CO+CO₂)均达到最大值,分别为4.3和3.2。     

光催化CO2还原为CH4研究进展(英文)

太阳能驱动二氧化碳光催化还原为CH₄是缓解全球变暖和能源危机的有效策略,然而,光催化效率较低以及产物选择性差,严重阻碍其大规模商业化应用。探究光催化CO₂还原反应机理对解决以上问题有重要参考意义,因此本文对光催化CO₂还原为C₁产物的基本原理及路径进行阐述,主要综述提高CO₂光还原效率以及CH₄选择性的方法,如构建异质结、设计结构缺陷、引入单原子催化剂以及其他方法,最后指出CO₂光还原CH₄面临的挑战和发展前景。     

羟基氧化铟团簇与二氧化碳和甲烷作用的密度泛函理论研究

二氧化碳(CO₂)和化石能源气体燃料甲烷(CH₄)均是化学稳定、 温室效应较大的分子, 因而对其活化、 转化和利用的研究具有显著的理论和实际意义. 本文采用密度泛函理论方法, 计算研究了羟基氧化铟团簇与CO₂, CH₄和(CO₂+CH₄)的作用. 结果表明, 氧化铟团簇通过其活性位点—In—O(桥氧)—对CO₂和CH₄分子进行[2+2]加成活化, 而羟基的引入调变了氧化铟团簇活性位点上的局部电荷, 显著降低了其与CO₂和CH₄分子作用的活化自由能垒, 使得CO₂和CH₄分子的活化变得容易进行. 活性位点—In—O(桥氧)—中的In, O上的局部电荷差值(q_In－q_O)越大, 其对CO₂和CH₄分子作用的活化自由能垒越低. 羟基氧化铟与CO₂和CH₄分子作用时, 电子由羟基氧化铟流向CO₂和CH₄分子(亲核活化); 而羟基引入前的氧化铟与CO₂和CH₄分子作用时, 电子则由CO₂和CH₄分子流向氧化铟(亲电活化).     

CO2重整CH4纳米ZrO2负载Ni催化剂的研究(Ⅱ)──催化剂组成与反应条件对催化剂性能的影响

研究了粒径为15～18nm的纳米ZrO₂-AS负载Ni催化剂对CO₂重整CH₄制合成气的催化性能,结果表明,Ni/ZrO₂-AS催化剂对重整反应的超常稳定催化作用不受Ni含量的影响,但当Ni质量分数低于10%时,催化剂活性随Ni含量增加而显著上升,此后,CH₄和CO₂的转化逐渐接近其热力学平衡值.高空速虽然降低了反应物的转化率,但可得到更高的时空产率.各种表征数据揭示,Ni/ZrO₂在结构上有别于传统的负载型催化剂,可看成是由尺寸相当(10～20nm)的纳米金属Ni和纳米ZrO₂形成的纳米复合物催化剂.     

天然铁矿石为氧载体的生物质化学链气化制合成气实验研究

在一个小型鼓泡流化床反应器上以Ar气为流化介质,对以天然铁矿石为氧载体的生物质化学链气化制合成气过程进行了研究。考察了反应温度对合成气组分、气体产率、碳转化率以及气化效率的影响,反应时间对合成气组分的影响;探讨了氧载体存在对生物质气化过程的影响。结果表明,天然铁矿石可以作为生物质化学链气化制合成气反应过程的氧载体,代替富氧空气或高温水蒸气作为生物质气化的气化剂;随着温度的升高,产物气体中CO、H₂的浓度逐渐增加,CO₂、CH₄浓度缓慢降低;随着反应时间的延长,合成气中H₂、CO、CH₄的相对浓度缓慢增加,而CO₂相对浓度逐渐降低;氧载体的存在能显著提高气体产率和碳的转化率及气化效率。扫描电镜-能谱(SEM-EDS)分析表明,当超过850 ℃时,铁矿石氧载体颗粒表面烧结现象明显,但反应前后,颗粒表面的成分及含量基本保持不变。     

大气压等离子体射流重整CH4-CO2制合成气

采用大气压等离子体射流,以CH₄和CO^₂直接作为放电气体进行常压下重整制合成气的实验研究,考察了等离子体射流的放电特征及放电距离、放电功率、原料气配比和流量对反应的影响。结果表明,该等离子体具有放电稳定、均匀的特征。重整反应的主要产物为合成气,只有少量的H₂O和积炭生成。优化的反应条件为放电距离为9mm,CH₄和CO₂的摩尔比为4/6。当原料气流量为1000mL/min,放电功率为88.4W时,CH4和CO₂的最高转化率为分别为94.99%和87.23%。甲烷和二氧化碳的转化率随放电功率的增加而增加,随流量的增加而减少。     

高稳定度CH4/CO2重整Ni/MgO催化剂的研究

用TPR,TPD,TPO,TPMC(程序升温CH₄解离积炭)和活性评价等手段研究了普通浸渍法与载体盐助分散浸渍法制得的CH₄/CO₂重整制合成气Ni基催化剂的性能.结果表明,用载体盐助分散浸渍制备的催化剂Ni-O-Mg间作用较强,吸附CO₂能力较大,CH₄解离积炭量少,因此其稳定性及寿命较好.     

Ir/SiO2上甲烷部分氧化制合成气反应的原位时间分辨红外和原位Raman光谱表征

采用原位时间分辨红外光谱和原位显微Raman光谱技术对Ir/SiO₂上甲烷部分氧化(POM)制合成气反应的初级产物和反应条件下催化剂表面物种进行了跟踪考察,实验结果表明,在H₂预还原的新鲜Ir/SiO₂表面,CO是V(CH₄):V(O₂):V(Ar)=2:1:45混合气反应的初级产物,因而甲烷的直接氧化过程是CO生成的主要途径;而在稳态反应条件下,CO生成的途径可能主要来自CO₂和H₂O与催化剂表面积碳物种(CHx)和/或CH₄的反应.催化剂上生成的积碳可能是导致稳态条件下Ir/SiO₂上POM反应机理不同于H₂预还原的新鲜催化剂的主要原因.     

Syngas production in a novel perovskite membrane reactor with co-feed of CO2

Partial oxidation of methane（POM） co-fed with CO₂ to syngas in a novel catalytic BaCo_0.6Fe_0.2Ta_0.2O_3-δ oxygen permeable membrane reactor was successfully reported.Adding CO₂ to the partial oxidation of methane reaction not only alters the ratio of CO/H₂,but also increases the oxygen permeation flux and CH₄ conversion.Around 96%CH₄ conversion with more than 93%CO₂ conversion and 100%CO selectivity is achieved,which shows an excellent reaction performance.A steady oxygen permeation flux of 15 mL/（cm² min） is obtained during the 100-h operation,which shows good stability as well.     

制备方法对Fe2O3/Al2O3-ZrO2在乙苯脱氢反应中催化性能的影响

为提高含铁催化剂的脱氢活性,采用浸渍法和一步沉淀法制备了Fe、Al和Zr含量相同的F4AZ10-imp和F4AZ10-pre催化剂,在550 ℃考察了其在乙苯CO₂氧化脱氢制苯乙烯反应过程中的催化性能,并结合XRD、N₂-吸附、NH₃-TPD、CO₂-TPD和H₂-TPR等表征手段对催化剂进行了分析。结果表明,与浸渍法相比,一步沉淀法制备的催化剂更有利于活性组分Fe₂O₃在催化剂表面的分散及反应物CO₂的转化。     

Synthesis of Cu-Ce0.8Zr0.2O2 catalyst by ball milling for CO2 reforming of ethanol

A Cu-Ce_0.8Zr_0.2O₂ (Cu-CeZr) catalyst was synthesized by a facile ball-milling technique and its performance towards to CO₂ reforming of ethanol was deeply studied. Noticeably, syngas production from ethanol dry reforming is regarded as one of the efficient routes to minify the undesirable CO₂ discharge. Various characterization and detailed experimental tests were conducted to probe the influence of catalyst preparation method. Hence, the as-prepared Cu-CeZr sample presented a better activity compared with Cu/CeZr prepared by precipitation method. Full ethanol conversion was achieved at as low as 550?°C under the conditions where only 49?mol% H₂, 41?mol% CO and 10?mol% CH₄ were formed as main products. Additionally, Cu-CeZr catalyst exhibited satisfactory stability even under severe stoichiometric feed composition (ethanol/CO₂?=?1) during 90?h on-stream aging tests. Herein, the remarkably superior catalytic performance of Cu-CeZr was interpreted in terms of the improved Cu dispersion and the intimated metal-support interaction. This might shed light on syngas production from an sustainable process instead of conventional methane dry reforming.     

K2CO3修饰的铁锆复合氧载体-煤焦化学链气化制氢反应特性研究

以K₂CO₃修饰的Fe₂O₃和ZrO₂复合型氧化物为氧载体(K3-Fe70Zr30),在固定床装置上考察了温度和原料配比对煤焦化学链制氢过程中产气率及组成的影响。程序升温实验结果表明,煤焦与氧载体500 ℃时开始反应,温度高于750 ℃时反应速率快速增大;而还原态氧载体与水蒸气400 ℃时开始反应,当温度高于500 ℃时出口氢气浓度明显增大。恒温实验表明,随温度升高,产品气中CO/CO₂体积比增大,导致产氢量降低。随煤焦与氧载体比例增加,产品气体中CO/CO₂体积比增加,而产氢量先增大后降低,其最大值可达1.734 L/g。K3-Fe70Zr30氧载体在前两次循环能维持良好的反应活性,但在第3次循环反应中活性降低,而重新添加K₂CO₃之后氧载体活性恢复,表明氧载体活性降低主要是由于K₂CO₃的流失所致。     

Production of Hydrogen-Rich Syngas from Biogas Reforming with Partial Oxidation Using a Multi-Stage AC Gliding Arc System

The aim of this research work was to evaluate the possibility of upgrading the simulated biogas (70?% CH₄ and 30?% CO₂) for hydrogen-rich syngas production using a multi-stage AC gliding arc system. The results showed that increasing stage number of plasma reactors, applied voltage and electrode gap distance enhanced both CH₄ and CO₂ conversions, in contrast with the increases in feed flow rate and input frequency. The gaseous products were mainly H₂ and CO, with small amounts of C₂H₂, C₂H₄ and C₂H₆. The optimum conditions for hydrogen-rich syngas production using the four-stage AC gliding arc system were a feed flow rate of 150?cm³/min, an input frequency of 300?Hz, an applied voltage of 17?kV and an electrode gap distance of 6?mm. At the minimum power consumption (3.3?×?10^?18?W?s/molecule of biogas converted and 2.8?×?10^?18?W?s/molecule of syngas produced), CH₄ and CO₂ conversions were 21.5 and 5.7?%, respectively, H₂ and CO selectivities were 57.1 and 14.9?%, respectively, and H₂/CO (hydrogen-rich syngas) was 6.9. The combination of the plasma reforming and partial oxidation provided remarkable improvements to the overall process performance, especially in terms of reducing both the power consumption and the carbon formation on the electrode surface but the produced syngas had a much lower H₂/CO ratio, depending on the oxygen/methane feed molar ratio. The best feed molar ratio of O₂-to-CH₄ ratio was found to be 0.3/1, providing the CH₄ conversion of 81.4?%, CO₂ conversion of 49.3?%, O₂ conversion of 92.4?%, H₂ selectivity of 49.5?%, CO selectivity of 49.96?%, and H₂/CO of 1.6.     

Conversion of natural gas to C2 hydrocarbons through dielectric-barrier discharge plasma catalysis

The experiments are carried out in the system of continuous flow reactors with dielectric-barrier discharge (DBD) for studies on the conversion of natural gas to C₂ hydrocarbons through plasma catalysis under the atmosphere pressure and room temperature. The influence of discharge frequency, structure of electrode, discharge voltage, number of electrode, ratio of H₂/CH₄, flow rate and catalyst on conversion of methane and selectivity of C₂ hydrocarbons are investigated. At the same time, the reaction process is investigated. Higher conversion of methane and selectivity of C₂ hydrocarbons are achieved and deposited carbons are eliminated by proper choice of parameters. The appropriate operation parameters in dielectric-barrier discharge plasma field are that the supply voltage is 20–40 kV (8.4–40 W), the frequency of power supply is 20 kHz, the structure of (b) electrode is suitable, and the flow of methane is 20–60 mL · min⁻¹. The conversion of methane can reach 45%, the selectivity of C₂ hydrocarbons is 76%, and the total selectivity of C₂ hydrocarbons and C₃ hydrocarbons is nearly 100%. The conversion of methane increases with the increase of voltage and decreases with the flow of methane increase; the selectivity of C₂ hydrocarbons decreases with the increase of voltage and increases with the flow of methane increase. The selectivity of C₂ hydrocarbons is improved with catalyst for conversion of natural gas to C₂ hydrocarbons in plasma field. Methane molecule collision with radicals is mainly responsible for product formation.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.     

Combined transformations of carbon dioxide and ethanol in the presence of the intermetallic compound TiFe0.95Zr0.03Mo0.02, Pd/SiO2, and Al2O3

The influence of the composition of catalytic systems and the method for H₂ feed into the reaction area on the degree of conversion of CO₂ during its joint transformations with ethanol and on the selectivity of formation of liquid organic products (ethyl acetate, acetaldehyde, and hydrocarbons) was studied atp=15 atm andT=573 K. A noticeable conversion of CO₂ and ethanol into ethyl acetate and acetaldehyde was observed in the presence of only the intermetallic compound, its composition with a palladium-containing catalyst, and the whole ternary catalytic system. The selectivity of the reaction changed when the binary catalytic composition consisting of the intermetallic and γ-Al₂O₃ was used. In this case, the fraction of C₉–C₁₄ alkenes and alkenes with normal and iso structures was mostly formed; its content was as high as 40%. The degree of conversion of CO₂ reached 30–36% and the selectivity to liquid products was 70–80% only when the hydrogen desorbed from the intermetallic was used. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1360–1364, July, 1998.     

Non-catalytic pyrolysis of ethane to ethylene in the presence of CO2 with or without limited O2

Influence of the presence of CO₂, which is a mild oxidant, on the performance of the thermal cracking of ethane to ethylene in the absence or presence of limited O₂ at different temperatures (750–900‡C), space velocities (1500–9000 h^-1) and CO₂/C₂H₆ and O₂/C₂H₆ mole ratios (0–2.0 and 0–0.3 respectively) has been investigated. In both the presence and absence of limited O₂, ethane conversion increases markedly because of the presence of CO₂, indicating its beneficial effect on the ethane to ethylene cracking. The increased ethane conversion is, however, not due to the oxidation of ethane to ethylene by CO₂; the formation of carbon monoxide in the presence of CO₂ is found to be very small. It is most probably due to the activation of ethane in the presence of CO₂.     

过渡金属修饰Fe2O3/Al2O3氧载体的Redox性能研究

采用冷冻干燥法分别制备了经Cu、Co、Mn、Ni修饰的Fe₂O₃/Al₂O₃氧载体。利用化学吸附仪,通过程序升温还原(H₂-TPR)和程序升温氧化(TPO)来研究经不同过渡金属修饰的Fe₂O₃/Al₂O₃与H₂和O₂的反应性能。实验发现,在Fe₂O₃/Al₂O₃中加入Cu、Co、Ni以后,氧载体与H₂的反应性都有提高,但是当在Fe₂O₃/Al₂O₃中加入Mn以后,氧载体的反应性和载氧能力反而下降。经Cu修饰的Fe₂O₃/Al₂O₃与H₂的反应性最高,且具有很好的反应稳定性,适合用于化学链燃烧。